The present invention relates to vessels having textured surfaces for growing animal cells, plant cells, micro-organisms and the like (xe2x80x98bio-substancesxe2x80x99) and to methods for their production.
Many bio-substances can he propagated in vitro in containers such as so-called xe2x80x98roller bottles,xe2x80x99 that is, cylindrical vessels, usually of glass or polystyrene, which are partially filled with a liquid medium comprising the bio-substances. The bottles are arranged to be rotated slowly about their longitudinal axes, promoting aeration, while the liquid medium provides nutrients to the bio-substances as they grow on the inner surfaces of the container.
Limitations in the efficiency of conventional procedures have hitherto been due to the relatively small surface area provided by the smooth interior of the container, as well as the fact that such surfaces do not provide optimum characteristics for the growth processes. It is an object of the present invention to eliminate or minimize these disadvantages.
Accordingly, in a first aspect of the invention, there is provided apparatus for use in a method of culturing micro-biological material, wherein said apparatus defines a rough or uneven growth surface arranged for contact with micro-biological material being cultured. An advantage of the inventive apparatus is that its use can allow cultured material to be grown at enhanced rates.
Preferably, the growth surface is rendered rough or uneven by surface features having a depth of 1 mm or less and, preferably, a depth of 0.1-0.5 mm. In preferred embodiments, the growth surface is pitted, or pockmarked with a plurality of craters or crater like depressions, preferably to depths of 1 mm, or less and more preferably to depths of 0.1-0.5 mm. Preferably, the craters or crater like depressions measure less than 5, preferably less than 2, and more preferably less than 1 mm across. Most preferably, the crater or crater like depressions measure less than 0.5 mm across.
In further embodiments, the growth surface is micro-cupellated and it can be formed from an organic polymer. The polymer can be coated onto a supporting substrate and, preferably, is a silicone rubber. In an embodiment, the growth surface forms an inner surface of a container for retaining biological material being cultured.
In a second aspect, the invention provides a method of culturing a micro-biological material, comprising culturing said material using apparatus defining a growth surface, wherein said material is in contact with the growth surface and the growth surface is uneven or rough. Advantageously the inventive method allows biological material to be grown at an enhanced rate.
Preferably, the apparatus employed in the second aspect of the invention is in accordance with its first aspect.
In a third aspect, the invention provides a method of providing a substrate with a textured surface comprising the steps of forming a mobile surface studded with a granular material on the substrate, setting the mobile surface and removing the granular material to leave a textured surface on said substrate.
In a fourth aspect of the invention, there is provided an article having a textured surface that can be obtained by a method according to the invention in its third aspect. Preferably, the article is a tissue or cell culture vessel, such as a roller-bottle.
In all aspects of the invention the biological material preferably comprises tissue, cells or like matter, including viral particles or virions.
In the invention according to its fourth aspect, the mobile surface is preferably tacky prior to the setting step, so as to promote adherence of the granular material. In a preferred embodiment, a (preferably solvent-less) silicone paint, designed for polymerisation to form silicone rubber, is applied to the interior surface of a glass or polystyrene roller bottle. While the coating is still in liquid form, common salt particles are injected into the container, for example, under pressure, to adhere to the prepared silicone coating, with any excess salt being removed again from the container. The coating is then allowed to polymerise into a solid layer at ambient or elevated temperature, depending on the type of silicone used. When hardened, the salt particles adhering to the coating are removed by dissolution in water, to leave a surface-porous layer exhibiting a cratered or micro-cupellated structure, as well as the special affinity for bio-substances of silicone rubber. The container so prepared is found to result in a greatly increased yield when used for growth processes in the manner described.
To promote adhesion of the silicone rubber layer within a glass or polystyrene container, a conventional adhesive, preferably a mineral spirit based primer, can be first applied to the surface prior to deposition of the silicone layer.
In embodiments of the invention, it is a prerequisite that the growth surface should be non-toxic and inert in respect of bio-substances and liquid media. The method of creating such surfaces should not involve any materials, which if remaining on the surface as impurities, could have a deleterious effect on the growth process.
In the above described method, various types of particles can be used in place of common salt, such as, for example, sugar, saltpetre and the like; however, common salt is preferred as being non-toxic and inert in respect of normal media and bio-substances, as well as being soluble in water for subsequent removal. Solubility of the particles in a non-toxic solvent is an important factor in their choice.
Attempts have been made to use xe2x80x98open-porousxe2x80x99 silicone rubbers, such as the material xe2x80x98Immobasilxe2x80x99 (xe2x80x98Immobasilxe2x80x99 is a registered trade mark); however, the results obtained were not as satisfactory as those achievable using the various aspects of the present invention. The open-porous structure (that is, the presence of inter-connected pores within the body of the silicone rubber) in such known materials leads to difficulties in the subsequent harvesting of the biosubstances from the interstices of the coating on completion of a growth cycle.
In an embodiment of the invention, surface pitting or cratering, for example, micro-cupels, can be produced in the inner surfaces of glass or polystyrene containers per se. For this purpose, salt or other suitable particles are injected, for example, pneumatically, into the container while the latter is at elevated temperature, either during its manufacture or on subsequent heating. Upon cooling, the particles are then removed as described above, leaving the interior surface of the glass or polystyrene container with a textured, cratered or micro-cupellated structure, again resulting in enhanced efficiency of the process. In the case of polystyrene containers, prior to use, the standard procedure of plasma treatment of the inner surface can be applied to impart a negative electrical charge to the surface, as required for the growth process. Other types of particle can be used apart from salt, the latter however, being again preferred for the reasons enumerated.
It is evident that other methods lying within the ambit of the invention may also be used to derive surface porous, cratered or micro-cupellated textured surfaces of the nature described for growing of bio-substances. The invention can equally be applied to all suitable containers, such as, for example, flasks, tubes, trays, roller bottles, plastic bags and the like.
In applications where very large area growth surfaces are required, it is conventional to utilize containers which comprise flat plates, for example, of polystyrene, wetted by the liquid medium, and upon which the bio-substances are made to grow. Such plates can also be provided with coatings of silicone rubber having a cratered or micro-cupellated, porous, surface structure according to the invention, in the manner described above, to result in substantially enhanced productivity.
Thus, roller bottles and other containers according to the invention can have a specially textured, cratered or micro-cupellated growth surface, usually an inner surface, suitable for use in the growth of bio-substances as aforesaid. By their nature, these surfaces are more conducive to the adhesion and growth of bio-substances, with resulting improved process efficiency. It is considered that the larger surface areas provided by such growth surfaces is a factor in their enhanced performance.
In order that the invention may be better understood, an example thereof will now be described by way of illustration only and with reference to the accompanying drawings, wherein;